國立政治大學應用物理所

演講時間：113年4月29日(一)13:10~14:10
演講地點：志希樓2F 理學院會議室

摘要：

The field of quantum optics has been evolving at a rapid pace since the discovery of direct-bandgap monolayer semiconductors, such as transition metal dichalcogenides (TMDs). In TMDs, compared to conventional bulks and quantum wells, a much stronger binding energy makes the excitons dominate the optical properties in an unprecedented way. This leads to a plethora of quantum photonics applications based on 2D materials. Such strong exciton binding also leads to a never-before-seen series of exciton Rydberg states observed at cryogenic temperatures. In this talk, I will highlight my recent works related to excitons, such as how to optically detect the quantum coherence of dark exciton Bose-Einstein condensate, how to produce a dark electron-hole pair in a quantum dot for quantum memory device, the full solution of exciton-polariton eigenstates that include all exciton Rydberg states. I will also discuss the latest work on a complex quasi-particle called exciton polaron, found by injecting carriers into semiconductor, that emerges as a correlated state of an exciton and a polarized Fermi sea of electrons (or holes) due to Coulomb interactions. I will show how the polaron state made of 1s or 2s exciton evolves with carrier density, and displays an energy dispersion minimum at finite momentum, reminiscent of the roton observed in liquid Helium 4. These results are calculated using the many-body theory we have developed and agree quantitatively with experiments on TMDs. Finally, I will discuss future prospects.

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